Selective formation of acetate intermediate prolongs robust ethylene removal at 0 °C for 15 days

Efficient ethylene (C2H4) removal below room temperatures, especially near 0  °C, is of great importance to suppress that the vegetables and fruits spoil during cold-chain transportation and storage. However, no catalysts have been developed to fulfill the longer-than-2-h C2H4 removal at this low temperature effectively. Here we prepare gold-platinum (Au-Pt) nanoalloy catalysts that show robust C2H4 (of 50 ppm) removal capacity at 0 °C for 15 days (360 h). We find, by virtue of operando Fourier transformed infrared spectroscopy and online temperature-programmed desorption equipped mass spectrometry, that the Au-Pt nanoalloys favor the formation of acetate from selective C2H4 oxidation. And this on-site-formed acetate intermediate would partially cover the catalyst surface at 0 °C, thus exposing active sites to prolong the continuous and effective C2H4 removal. We also demonstrate, by heat treatment, that the performance of the used catalysts will be fully recovered for at least two times.


Supplementary Note 1 | Comparisons of the results under different C2H4
concentrations and flow rates for catalytic C2H4 removal on Au54Pt46/ZHM20 catalyst. Fig. 10).

(I) Comparisons of the results under different C2H4 concentrations (Supplementary
-(i) One can see, with the higher concentration of C2H4 we applied, the quicker decrease of C2H4 removal efficiency in the first several hours. This could reflect the adsorption curve of the ZHM20 support.
-(ii) When the curve reaches the minimum point, the catalytic reaction for converting C2H4 may start and the removal efficiency increases again, thus showing a U-shape curve.
-(iii) We noted, with a low C2H4 concentration of 25 ppm, that the catalyst shows a delay activation than that of 50 ppm C2H4, suggesting the transport limitation under the condition of 25 ppm C2H4, in which the catalytic reaction is slower than that of 50 ppm C2H4.
-(iv) The similar removal efficiency in the steady state under conditions of 25 and 50 ppm C2H4 suggests the catalyst may have a maximum removal efficiency of ~80% under the flow rate of 10 mL min -1 . This may also be due to the transport limitation.
-(v) We further found, in the high C2H4 concentration case (100 ppm C2H4), that the removal efficiency is about half of that of 50 ppm C2H4 (Supplementary Fig. 11). This suggests a similar catalytic rate in both conditions. Fig. 11).

(II) Comparisons of the results under different flow rates (Supplementary
-(i) When we increased the flow rate in C2H4 removal experiments to 20 mL min -1 , in which the space velocity is 6000 mL h -1 g -1 , we can observe, with the higher flow rate we set, the quicker decrease of C2H4 removal efficiency is observed in the first several hours. This could reflect the adsorption curve of the ZHM20 support.
-(ii) We found the C2H4 removal rates are similar at both flow rates, indicating the flow rate may have negligible influence on the activity of Au54Pt46/ZHM20 catalyst.